There are several individual projects in this program. Each project deals with an aspect of respiration during the development of the individual. Project A is concerned with the effects of exercise upon gas transport during pregnancy. Project B is concerned with investigating the biochemical and physiological characteristics of uterine renin and with the role of renin in the regulation of uterine blood flow. Project D is concerned with investigating the effects of incubator gas concentrations upon the development of the avian embryo. Project E is oriented toward measuring the distribution of fetal cardiac output using chronically catheterized sheep. In Project F we are investigating mechanisms controlling fetal water balance in chronically catheterized sheep fetuses. Project J focuses upon the effects of respiratory depression during pregnancy, using female methadone addicts as subjects and we are developing an animal model for the methadone maintenance syndrome.